Production of bright nickel deposit



im licated Jan. M, 1941 accuser rnobbcrron or nnionr sienna nnnosrr Meyer h. lirced, rtnsonim iil'onn, assigimr to the Scymourllianuiacturlng idol, dcyinour, iilonni l lo harassing, application ,l'annary til, litid,

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"this invention relates to an addition agent ior nickel plating baths, which causes to be produced on articles plated therein a direct, all-metallic, bright nickel deposit or new and unusual cast,

and to the plating process using said agent and Q lending and polishing the article to give the nickel lid deposit a bright, glossy, lustrous appearance. in the attempt to obtain this bright, lustrous appearance as a direct result oi the plating operation, there have been included in the ordinary nickel electro-plating baths certain addition agents oi organic origin, colloidal in character, such as glycerin, gum tragacanth, dextrlne', glucose, gum arable, casein, egg albumin, terpenes, terpene alcohols and aldehydes, natural and synthetic gums and resins and the like, and complex nickel compounds oi aromatic sulphonates.

lhe use of such addition agents is accompanied with serious drawbacks. Extreme care must be observed to avoid any excess of these agents in the plating solution creating great dimculty in the operation of such. nickel plating baths. Ercesses oi these agents void the utility of the bath and even a small excess promotes peeling or,

cracking oi the deposit. Yet methods oi analysis are inadequate ior accurate and such rigid control oi the plating bath composition and are iar too cumbersome, time consuming and expensive ior practical purposes. Furthermore, due to cataphoresis coupled with capillary action. and adsorption, organic material is retained in all oi the nickel coatings deposited iromplating baths containing such addition agents. its a result, deposits obtained thereirom are not suitably dense, are readily subject to pitting and have reduced resistance to corrosion; are brittle and not suitable ior iurther working. Consequently, such deposits are unsatisiactory as a base deposit to be subsequently covered with chromium plate or with a coating of any other metal.

in addition to the above shortcomings, at their best, deposits produced in the presence oi the above addition agents are unattractive as a finish coat by themselves because oi their yellowish, White shade.

likewise, bright nickel coatings that are produced by buirlng and polishing are unattractive because of their yellowish hue and also have a tendency to reducethe throwing power of any subsequent deposit of chromium or other metal.

Thus one feature of my invention is the introduction of an addition agent for a nickel plating bath to enable the direct electrodeposition therefrom of an all-metallic bright nickel deposit reouiring no bufiing or polishing to develop its glossy, lustrous appearance.

ii. second ieature is the development at an addition agent or brightener tor a nickel plating bath, the composition and concentration at Which agent in the plating bath may be very readily and easily adjusted and determined.

Another ieature is the direct deposition irom a nickel plating bath oi a bright, iustrom, hard, ductile, dense, non-porous nickel deposit oi any suitable thickness, and enhibitlng good adher ence'and resistance to corrosion and abrasion it iurther feature is the addition to a nickel plating bath or an agent that improves the gen eral efficiency oi the bath and causes the throwing power oi any subsequent deposits oi chm-=- mium or other metal over the nickel to be increased.

Still another ieature is the production oi a direct brightnickel deposit having a bluish tinge suitable as a iinal finish. in itseli or as a suitable base ior subsequent deposit oi chromium plate.

Other objects and ieatures oi my invention Will occur from the following more detailed description thereoi.

in general, my invention consists in the addi-- tion to a nickel plating bath oi an addition agent comprising a preferably soluble, suitable mlirture oi a compound oi cobalt and a compound oi at least one other metal selected iroin the group consisting of cadmium, zinc and mercury in such relative proportions and in sumcient amount to bring about the deposition irom the bath, upon the passage of an electric current irorn an anode throughsaid bath to a cathode, oi a bright nickel deposit upon the cathode, under the particular operating conditions. The addition agent or brightener comprises the mixture oi the compound oi cobalt and the compound of at least one other metal selected irorn the group consisting of cadmium, zinc and mercury, either in the solid state or in solution. Whether in the solid form or in solution, the brightener may include, in addition tothe suitable combination oi the above described metal compounds, other soluble compounds which upon the introduction of the brightener to the plating bath react to assist in anode corrosion, decrease polarization at the anode, increasethe conductivity oi the bath, prevent the formation oi basic compounds and assist in the adjustment oi the hydrogen ion concentration oi the bath. For brevity in the specification and in the claims, these. other soluble compounds will be reierred to as other compounds to efiect the plating bath characteristics. it is understood that this general definition shall suffice to include compounds effective for any or all of the purposes herein enumerated.

Particularly satisfactory results are obtained with an addition agent mixture which has for its metallic ion yielding constituents a soluble salt of cobalt and of cadmium.

Any soluble cobalt and cadmium, and/or zinc or mercury salts suitable for electroplating may be used in the preparation of my brightener or addition agent, for example, the chlorides or sulphates.

As nickel plating solutions vary in composition, a wide variation in ratio of metallic cobalt constituent in the addition agent to metallic cadmium and/or zinc or mercury constituent is possible. Preferably, the metallic cobalt may be present in from about 99 to about 25 parts thereof to from around 1 to about 75 parts of metallic cadmium and/or zinc or mercury.

Suitable salts for assisting in anode corrosion are ammonium salts, such as the chloride, sulphate, and the like; nickel salts, such as nickel chloride, sulphate and other soluble nickel plating salts. The ammonium salts are also effective in and may be added for decreasing the polarization at the anode and for increasing the conductivity of the plating bath. Nickel chloride and sulphates such as those of sodium and magnesium are also effective for increasing the conductivity of the plating bath.

The formation of basic substances may be pre- Q vented by including in the addition agent a suitable amount of sulphuric acid.

The addition agent may also contain, for the purpose of assisting in adjusting the hydrogen ion concentration of the plating bath, a. suitable quantity of a compound ordinarily added to the bath for such purpose such as boric acid, mineral acid, e. g., sulphuric acid, or an organic acid such as citric acid.

I have found that with the more commonly met nickel plating baths, very good results are obtained when there is added thereto a brightener or addition agent which contains any suitable cobalt and cadmium salts in such proportions that the metallic elements are present in the ratio of about 7% parts cobalt to about 1 part of cadmium. The cadmium may be replaced in whole or in part by zinc and/or mercury in this same ratio to give the same results, as indi cated hereinabove.

The following examples further illustrate the invention, but the invention is not restricted to these examples:

Example 1 A good brightener or addition agent consists of 14.4 parts of commercial crystal cobalt chloride and 1 part of commercial crystal cadmi chloride.

-Example 2 A typical formula for the brightener containing other salts to 'eflect anode corrosion, conductivity, and the pH of the plating bath, and to prevent the formation of basic compounds is:

In general, only a small concentration of the brightener according to the present invention in the plating bath is necessary toyield desired results.

Examples of typical plating operations and the solutions therefor including my brightener are:

Example 3 Ounces per gal. Nickel sulfate 16 Ammonium chloride 3.5 Boric acid 3 Brightener of Example 2 Such a. plating bath has a pH value of 5.6. Operating at about 104 F. under a current density of about 8 amperes per sq. ft., it gives a very satisfactory direct bright nickel deposit.

Example 4 Ounces per gal. Nickel sulfate 36 Ammonium chloride 3.5 Boric acid 3 Brightener of Example 2 This plating bath, showing a pH value of 4.4, allows a good, rapid production capacity when operated at a current density around 36 amperes per sq. ft. at a temperature of about 123 F.

Example 5 Nickel ammonium sulphate 12 Nickel sulfate 1 4 Boric acid 3 Ammonium chloride 4.5 Sodium chloride 0.8 Brightener of Example 2 0.4

having a pH value of 5.5.

The above, examples are suitable for adjustment of typical nickel plating baths by addition of my brightener. They are given by way of illustration only and it is not intended to limit the invention thereto.

Plating baths, such as shown in the examples, made up initially with the constituents of the brightening addition agents in about the concentrations set forth, may be operated for an extended period depending upon output of plated products without any replenishment of brightener. When. after such extended operation, the deposit obtained appears to be of insufllcient brightness, a suitable quantity of brightener may be added to the bath.

However, a nickel plating bath can be operated according to my invention without replenishing the addition agent until the anode is entirely consumed if for the ordinary nickel anode there is substituted a nickel anode containing such proportions of cobalt and at least one other metal selected from the group consisting of cadmium, zinc or mercury as will yield a bright nickel deposit on the cathode. Generally, the proportion of cobalt contained in the anode of my invention is greater than that ordinarily occurring as an impurity in the usual nickel anode.

In plants employing plating baths under other operating conditions as to nickel content, concentration of other ions, hydrogen ion concentration, temperature and current density. the most desirable ratio of cobalt to cadmium and/or zinc or mercury for the conditions may readily be arrived at by a few short experimental test runs easily followed by observation of the changes as the dullness decreases and the proper degree of brightness or the deposit is developed. Thus any nickel plating bath can be readily made up with fill Til

2,228,991 J c nickel, which comprises passing an electric curslich relative proportions and concentrations oi the cobalt and cadmium and/or zinc or mercury suitable to yield a bright nickel deposit therefrom under the particular operating. conditions observed.

The desired proportions of the brightening agent are very readily controlled by quick, easy and simple methods within the comprehension of the type of help ordinarily employed in a plating plant. Such methods are generally dependent solely on metallic constituents.

By the use of my brightener or addition agent. there is deposited with the nickel small amounts oi the other metals, such as, cobalt and cadmium and/or zinc or mercury, the sheet of which is to so influence the character of the deposit so that it possesses a direct bright, lustrous appear ance requiring no subsequent mechanical treatment. The deposit also has a desirable bluish cast, generally approaching the color of a chromium deposit. it is dense, non-porous, compact, ductile and highly resistant to abrasion and corrosion, and highly adherent.

The type oi deposit obtained in accordance with the present invention has a marked tendency to enhance the throwing power at any subsequent deposit at chromium or other metal. Because oi its characteristic and unusual color, it is well suitable for use as a finished plate by itself as well as to serve a base coat tor a subsequent chromium deposit.

While specific embodiments of my invention have been described tor purposes of illustration only, it is to be understood that the invention is not to be restricted thereto, but that it is only to be limited in accordance with the scope of the following claims in the light oi the prior art.

I claim:

i. an aqueous, acid nickel sulfate (selected irom the group consisting of nickel sulfate and nickel ammonium sulfate) plating bath, the electrolyte of which comprises in addition to the nickel ions, at brightener consisting of ions oi (or cobalt and of (b) at least one other metal'selected from the group consisting of cadmium, zinc and mercury in the proportion approximating about seven and one-quarter parts of cobalt to about one part of the single or combined metals of (b).

2. an aqueous, acid nickel sulfate (selected irom the group consisting of nickel sulfate and nickel ammonium sulfate) plating bath, the electroylte of which comprises in addition to the nickel ions, a brightener consisting of ions of cobalt and oil cadmium in the proportion approximating about seven and one-quarter parts of cobalt to about one part of cadmium.

3. An aqueous, acid nickel sulfate (selected from the group consisting of nickel sulfate and nickel ammonium sulfate) plating bath, the electrolyte of which comprises in addition to the nickel ions, a brightener consisting of ions of cobalt and of zinc in the proportion approximating about seven and one-quarter parts of cobalt to about one part oi zinc.

l. An aqueous, acid nickel sulfate (selected from the group consisting of nickel sulfate and nickel ammonium sulfate.) plating bath, the electrolyte of which. comprises in addition to the nickel ions, a brightener consisting of ions of cobalt and of mercury in the proportion approximating about seven and one-quarter parts of cobalt to about one part of mercury.

5. The process of electrodepositing bright rent from a nickel anode containing cobalt and at least one other metal selected from the group consisting of cadmium, nine and mercury through an aqueous, acid nickel sulfate (selected from the croup consisting of nickel tuliate and nickel ammonium sulfate) platlna bath to a cathode, the cobalt and at least one other metal item the group of cadmium, nine and mercury being pres ent in said nickel anode in such relationship as to be introduced into the bath as a brightening aeent and in. the proportion approximating about seven and one-uuarter parts at cobalt to about one part of the sincle or combined metals oi the group cl, zinc and mercury.

c. the process at electrodepositina bright nickel, which comprises passion on electric current irom a nickel anode containina cobalt and cadmium through auueous, acid nickel sul late (selected irom the proup consisting oi nickel sulfate and nickel monl sullate) plating bath to a cathode, the cobalt and cadmium beinu present in said nickel anode in such relationship as to be introduced into the both as a brighten inc" agent and in the proportion appronimatina about seven and one-quarter parts oi cobalt to about one part at c.

l. The process oi elec mepositina bright nickel, which comprises passion on electric current from a nickel anode containing cobalt and nine through an aqueous, acid nickel sulfate (selected from the croup consistine of nickel suliate and nickel mu sulfate) plating bath to iii hill

a cathode, the cobalt and mac being present in i said nickel anode in such rtionsliip as to be introduced into the bath as a brightening agent and in the proportion approatlng about seven and one-quarter parts oi" cobalt to about one part oi cine.

d. The process at electroplating bright nickel, which comprises passing an electric current irom a nickel anode containing cobalt and mercury through an aqueous, acid nickel sulfate (selected from the group consisting of nickel sulfate and w sulfate) plating" bath to a cathode, the cobalt and mercury being present in said nickel anode in such relationship as to be introduced into the bath as a brightening agent and in the proportion approximating about seven and one-qua parts oi cobalt to about one part oi mercury,

b. The process at electrodepositing bright nickel, which comprises passing an electric current irom an anode to a cathode through an aqueous, acid nickel sulfate (selected from the group consistina oi nickel suliateand nickel ammonium sulfate) plating bath in the presence in from the eroup consistina of cadmium, zinc and mercury in the proportion approximating about lid seven and one-quarter parts at cobalt to about nickel; which comprises passing an electric current fromv an anode to a cathode through an aqueous, acid nickel sulfate (selected from the group consisting oi nickel sulfate and nickel ammonium suliate) plating bath in the presence in said bath of a brightener consisting of cobalt ions and of mercury ions in the proportion approximating about seven and one-quarter parts of cobalt to about one part of mercury.

MEYER L. FREED. 

